General uncontroversial cleanup:

- Made private methods static where possible (runtime can elide checking the object for null).
- Declared attribute classes as sealed (allows reflection on attributes to complete faster).
- Moved some static cctor's into field initializers (static cctor's are slower than static field initializers).
- Made classes static if they contained only static methods (can't create instances of useless objects).
- Use inferable Exts.Lazy and not new Lazy<T>().
- Added required STAThread attribute to CrashDialog.
- Removed unused parameters in private methods.
- Added Serializable attribute to exceptions.
- Added parameter name in calls to ArgumentNullException.
- Use of as operator instead of is + cast.
- Changed (x as Foo).Bar anti-pattern into ((Foo)x).Bar. Results in sensible cast exceptions on error rather than null dereferences.
- Removed unused method in NullShader.

OpenRA.Game/Primitives/Bits.cs

@@ -17,9 +17,7 @@ namespace OpenRA.Primitives
 	static class BitAllocator<T> where T : struct
 	{
 		static int nextVal = 1;
-		static Cache<string,int> bits;
-
-		static BitAllocator() {	bits = new Cache<string, int>( _ => Allocate() ); }
+		static Cache<string, int> bits = new Cache<string, int>(_ => Allocate());
 
 		static int Allocate()
 		{